presented the English courts with novel legal questions. Under the lex mercatoria slaves were sometimes treated as chattels, with few if any rights, but the English courts did not always recognise mercantile custom as law, and even in English mercantile law, the subject was disputed. The question arose in English courts because personal actions could be laid in England even if the cause of action arose abroad. In 1698, an act of parliament opened the slave trade to all English subjects. In the 18th century, owners in England would advertise their sales of African slaves and also for the return of runaway slaves. Butts v. Penny and Defining People as Property In 1677, after the Royal African Company went bankrupt, the high court of King's Bench intervened to change the legal rationale for slavery from feudal law to the law of property. In 1677 in Butts v. Penny the courts held that an action for trover (a kind of trespass) would lie for black people, as if they were chattels. The rationale was that infidels could not be subjects because they could not swear an oath of allegiance to make them so (as determined in Calvin's Case in 1608). As aliens, they could be considered as "goods" rather than people for purposes of trade. Chief Justice Holt rejected such a status for people in Harvey v. Chamberlain in 1696, and also denied the possibility of bringing an assumpsit (another kind of trespass) on the sale of a black person in England: "as soon as a negro comes to England he is free; one may be a villein in England, but not a slave." It is alleged that he commented as an aside in one case that the supposed owner could amend his declaration to state that a deed was created for the sale in the royal colony of Virginia, where slavery was recognised by colonial law, but such a claim goes against the main finding in the case. In 1706 Chief Justice Holt refused an action of trover in relation to a slave, holding that no man could have property in another, but held that an alternative action, trespass quare captivum suum cepit, might be available. Ultimately the Holt court decisions had little long-term effect. Slaves were regularly bought and sold on the Liverpool and London markets, and actions on contract concerning slaves were common in the 18th century without